Film folding and supplying apparatus for stretch film packaging machines

ABSTRACT

The guiding means which provide to the pleating of the film (F) unwound from the bobbin and inserted in the packaging station, in order to adapt the width of the same film to the width of the products to be packaged, use rows of wheels ( 9, 9′, 15, 15′ ) to co-operate with the same film with rolling friction. The width of the pleated film may be adjusted by only adjusting of the reciprocal distance between the guides of lateral folding ( 13, 13′ ), and the corresponding rows of wheels ( 15, 15′ ). Before reaching between the folding guides, the packaging film runs on the convex portion of a transmission structure with an internal angle of about 170°, formed by a short central roller ( 5 ), and by long lateral rollers ( 105, 105 ′), all of them freely rotatable, which maintain the film transversally stretched and centered in correct manner on the following folding means. The roller ( 19 ) which maintains the lateral edges of the pleated film bearing on rubberised rollers ( 4, 4′ ) placed at the outlet of the folding means, is provided with free-wheels, thanks to which this unit of rollers may rotate only in the travelling direction of the film and not in the opposite direction. The pleated film which comes out from the said rollers ( 4, 4′, 19 ) arrives to a particular comb-shaped distributor, provided with electromagnets ( 31, 31 ′) that, when are deactivated allow to the film to freely run through said distributor and when are activated, transversally stop the same film between strips of rubber ( 29, 37 ) carried by the opposite jaws of the same distributor.

The invention relates to constructive improvements in the film foldingand supplying unit for the machines described in the Italian patent n. 1266 296, property of the same applicant, to which is made widereference. In this type of machines, the packaging film has a widthwhich is suitable to the packaging of products which have variabledimensions inside a large range and its width is proportionate to thatof the products having the greatest dimension that the machine can wrap.The width of the film is adapted to the dimensions of the product to bewrapped, with a process of pleating of the same film during the feedingphase to the wrapping phase, so that the longitudinal axis of the pleatsresults to be oriented in the length direction of the portion of filminserted in said station and such that the in the packaging of productshaving small dimensions, it is in any case provided for the formation ofa wrapping which is enough wrapped and blocked. In this type ofmachines, the film is unwound from the feeding bobbin, passes trough thetightening pulley which provides a longitudinal tensioned feeding andthen is transmitted on a transversal and arched roller whichtransversally tensions the same and avoid the formation of uncontrolledpleats because the film is coming out from said roller with an ascendingdirection and runs longitudinally with an own center portion, on arectilinear guide anteriorly provided with an idle roller whichfacilitates the entry of the film the lateral edges of which are foldedunder said guide by means of respective lateral guides, the whole insuch a manner that the film results folded with a pressed omegatransversal shape, and presents in such manner a width which isproportionate to the width of the product to be wound. Said curvedtransmission roller has been resulted of difficult realisation so thatit has been thought to substitute the same with a composite rollerformed by a central roller and two long lateral rollers, having the samedistance from the central roller with an angle of about 170°. Anotherdrawback found in the apparatus of the known type, is due to the greatcontact surface of the film with the folding guides above mentionedwhich were realised with polished metal or with material having a lowfriction coefficient. To improve the folding action performed by theguides, the same have been provided on the edges which was beforeoperating in contact with the film, with rows of idle wheels with whichthe film is co-operating with rolling friction.

The lateral edges of the film which is coming out from said foldingwhich are external to the folded portion of the said film, run uponrubber and idle rollers upon which the same are maintained in contact bya contrast superior roller, idle, but made of metal and sprung, afterthat the folded film arrives to a gripper-shaped distributor, made by alower fixed portion, to which there is fixed in projecting manner saidlongitudinal and central guide, and by an upper portion assembled upon astructure which may oscillates upon an anterior axis which is parallelto the same distributor, and which is carrying the final folder of themachine, the one which is folding on the bottom of the product the lastportion of film previously retained by the same distributor, and whichis carrying the heated conveyor for the welding of the lower edges ofthe packaging. This structure may be raised with oscillation upon saidtransversal axis, in the initial phase in which the film coming from anew bobbin must be inserted in a machine. Upon this structure there isassembled said metallic and sprung roller which co-operates with saidrubberised rollers. The distributor of the film realised with the knowntechnique, is complex and scarcely reliable, so that a further object ofthe invention is to improve the distributor and to provide freewheelmeans in the upper metallic roller contrasting the rubberised rollers,in such a manner that the film which passes through said rollers mayonly go forward and not backward.

In the apparatus of the described type, both folding guides of thelateral edges of the film fed by the machine, and the rubberisedrollers, are pre-arranged to be automatically adjustable in thereciprocal distance by means of self-centring regulation mechanism,controlled by an electric step motor controlled by the computer of themachine which by means of the optical barriers detects the dimensions ofthe products to be packaged, to automatically adjust to these the widthof the packaging film. It has been find out that it is possible torealise packaging machines more economic and able to give the samequality of packaging of the above mentioned machines, using rubberisedcontrast rollers having a sufficient length and with static positioningand pre-arranging the guides for the folding of the edges of the filmfed by the machine, with a manual regulation of the reciprocal distance.The products that the packaging machine may process are dimensionallydivided in two groups, the group of the medium-small products and thegroup of the large products and for each group of products there areused film bobbins of different width, naturally more wide for the groupof wide products, so if the machine had to pass from the operation of agroup of products to another group of products, the bobbin of the filmis changed and the pleating means of the same film are adjusted insuitable manner. When the machine is pre-arranged for the processing ofa group of products, the width of the folded film is chosen with regardto the width of the products having the smaller dimensions of that groupand the width of the pleated film may be adjusted or remain constant,both for working of the small products and for the large ones of thesame group.

These and other features of the improvements which is referred to andthe is advantages deriving therefrom, will appear better evident fromthe following description of a preferred embodiment of the same, made byway of non-limiting example, with reference to the figures of theattached sheets of drawings, in which:

FIG. 1 is a plan view from the top of the improved apparatus which isreferred to, without the overhanging structure which carries the sprungroller opposed to the rubberised rollers and the upper comb of the finaldistributor;

FIG. 2 shows other details of the apparatus longitudinally sectionedalong the line II-II of FIG. 1;

FIG. 3 shows the complete final distributor of the film as from FIG. 2,in closing position and sectioned along the line III-III of FIG. 1;

FIG. 4 shows other details of the apparatus transversally sectionedalong the line IV-IV of FIG. 1;

FIG. 5 shows further details of the distributor sectioned along the lineV-V of FIG. 2.

It must be stated that the terms front and rear are here considered withreference to the running direction of the film, therefore it will bedefined as front that portion which for the first is interested from thesame film in its advancement. In FIGS. 1 and 2, with numeral reference 1is indicated the horizontal traverse fixed with its ends to the sides ofthe frame of the machine, transversally to the path of the film F andwhich is carrying the lower jaw of the distributor of the same film, asmentioned after. In the centre line of the front of the traverse 1,there is projecting fixed, by means of screws 2, the enlarged end 203 ofthe longitudinal member 103 of a ribbed structure 3 which has in plant across shape which is longitudinally downwardly inclined, upon said end203 being rotatably assembled the intermediate portion of a shaft 104which is parallel to the traverse 1 and on the ends of which there arekeyed the rubberized and equal rollers 4, 4′, which support the lateraledges of the film which is coming out from the folding means furthermentioned. The rollers 4, 4′ have a length which is superior to theseprovided in the known art and their reciprocal distance remains the sameupon variations of the products to be packaged. The most lower end ofthe longitudinal member 103 of the structure 3 ends with a forkconformation 303, which in its interior supports projecting androtatably a roller 5 and which with its sides, which are diverging andinclined of about 8°-10° supports rotatably longer and equal rollers105, 105′, that with the roller 5 make a convex transmission whichsubstitutes the arcuate roller in the prior art, upon which istransmitted the film unwound from the bobbin and coming from thetensioning pulley, to be transversally stretched, to be maintainedcentred on the following folding means and to be pre-arranged in thebest manner for the co-operation with said means.

The longitudinal member 103 of the structure 3, carries superiorlydistributed projections 6 upon which there is fixed with screws 7 thelongitudinal and median portion of a plate 8 with rectangular planshape, having suitable dimensions, the longitudinal edges of which areslightly upwardly inclined and freely support rotatably rows of wheels9, 9′ with a rounded shape, which are suitable projecting from saidsupport edges of the plate 8, to substitute these in the guiding of thefilm during the folding phase. At the end of each rows of wheels 9, 9′,and in conditions of substantial tangency with the external edge ofthese, the plate 8 supports plates 10, 10′, with edges which aresuitably rounded and with a low friction coefficient with the film. Inthe centre-line of the anterior end of the plate 8 there is inferiorlyfixed, and with a longitudinal arrangement, a support 11 which isanteriorly projecting from the same plate to rotatably support a side byside couple of rollers 12 having the same dimensions, the general widthof which is substantially equal to the width which exists between theexternal sides of the rows of wheels 9, 9′. The film which leaves by theconvex transmission means made by rollers 5, 105 105′, is resting withits median and longitudinal band on the sliding structure made by therollers 12 and by the wheels 9, 9′ and the same film is folded undersaid rows of wheels, by the convex sides of guides 13, 13′, reinforcedby upper and longitudinal inserts 14, 14′ and provided with intermediateappendices 113, 113′ for the outside extension, with which said guidesare fixed at the ends of the transversal arms 403, 403′ of the crossstructure 3 above mentioned (see further). The convex edges of theguides 13, 13′ carry a slightly downwardly bent portion, under whichthere are fixed the one following the rows of wheels 15, 15′ of the samekind of those with numeral reference 9, 9′, which with the exception ofthe first ones are projecting from said edges for the cooperation withrolling friction with the lateral edges of the film F which for theco-operation with said means, is folded under the guiding median complexformed by the portions 8, 9, 9′, as it appears from FIG. 4, in such amanner to take an omega transversal shape. From FIG. 4 it is clear howthanks to the slight inclination of the axles of the rows of wheels 9,9′ and 15, 15′, the film touches only a portion of the circumference ofthe said wheels and it is distant from the superior and inferior facesof the same wheels. From FIGS. 1, 2 and 4 it is noted that the arms 403,403′ of the structure 3 are also ribbed with a U overturned shape andterminate with flat and enlarged appendices upon which there areprovided at different distances from the longitudinal member 103 of thesame structure 3, couples of threaded holes 16, 16′ in which there canbe fixed corresponding couples of screws 17, 17′ which are fixing inworking position the guides 13, 13′ with the relative rows of wheels 15,15′. The screws 17, 17′ pass through corresponding slots 18, 18′obtained on the guides 13, 13′, with a perpendicular orientation to thetravelling direction of the film F. In the FIGS. 1 and 4, the screws 17,17′ are positioned on the more internal holes 16, 16′ and are abuttingagainst the external ends of the slots 18, 18′, in such a manner thatthe guides with the rows of wheels 15, 15′ are in the position ofmaximum folding of the film under the central guide with the rows ofwheels 9, 9′ If required, the screws 17, 17′ may be positioned on themore external couple of holes 16, 16′, and the slots 18, 18′ may becarried against with said screws, with their internal ends, in such amanner that the rows of wheels 15, 15′ result to be substantiallypositioned outside of the rows of wheels 9, 9′. It is clear thatdepending on the film used and on the product to be packaged, the guideswith the rows of wheels 15, 15′ may be placed in any intermediateposition comprised between the extreme positions above mentioned.

From FIGS. 1, 2 and 4 it is noted that the film which is coming out fromthe described folding means, is transversally surmounted by the steelsprung roller 19 which pushes the edges of the same film on rubberisedrollers 4, 4′ and as mentioned in the introduction of the presentdescription, it is now assembled upon its support axle, with theinterposition of free-snap wheels, in such a manner that the film mayonly move forward between said rollers, and not recede. The sprungroller 19 is assembled on the sides of the know type structure 20 whichcarries the motorised conveyor 21 for the displacement of the packagedproducts and for the thermo-welding of the lower edges of the packagingfilm and that in co-planarity conditions with the upper portion of thesaid conveyor, supports motorised rollers 22 which are parallel betweenthem and to the said roller 19, between which there is co-planarlyarranged the fixed runner 23 provided with a recess 123 downwardly open,which houses the toothed saw 24 (FIG. 5) against which is pushed thepackaging film by means of a parallel and grooved lifter, not shown.Structure 20 is anteriorly fulcrumed to the frame of the machine, withlateral hinges 25, in such a manner that can be raised together with theroller 19, to facilitate the introduction of the film between thefolding means each time that the bobbin of the packaging film must bereplaced and the same film must be correctly transmitted between thesame folding means described.

From FIGS. 1, 2 and 5 it is noted that the traverse 1 is placed with itsupper wall at a level which is slightly superior to that of the filmwhich is passing between the rollers 19, 4, 4′, has the rounded edgesand the same traverse 1 is anteriorly and superiorly open with a recess26 which has substantially the same length of the distance which passesbetween the external sides of the rollers 4, 4′ and in which there isfixed with the screws 27, a jaw 28 having the shape of a small squaremember, the upper wall 128 of which is co-planar to the one of thetraverse 1 and is comb-shape, with the teeth oriented and opened in thetravel direction of the film. Upstream of the comb 128, the upperportion of the traverse 1 carries a recess which is parallel to the samecomb, in which there is housed, not projecting a rubberised groovedinsert 29 which is blocked in situ for example by means of end screws30. Outside of the unit 28, 29, at a short distance from its ends, onthe traverse 1 are is superiorly provided recesses which houseelectromagnets 31, 31′ (see also FIG. 3). Over of the traverse 1, at ashort distance and parallelly to this one there is arranged with itsflat and toothed portion which forms a comb 132 complementary to thelower comb 128, a jaw 32 L-shaped to resist to the bending-torsionstresses, which is upwardly raised with its anterior ribbed portion,which is provided at least on the ends with transversal ribs 232, 232′,and which is carrying laterally pins 33. 33′, which are parallel totheir longitudinal axis and corresponding with the point of the teeth ofthe comb 132, which with the same jaw which is referred to is fulcrumedat corresponding supports 34, 34′, fixed to the sides of the structure20. The jaw 32 carries at its end, onward extension appendices 332,332′, pre-arranged in such a manner that on the same may operate the endof springs for downwardly urging, which maintain said appendicesattested against lower and adjustable retainers 36, 36′ fixed to thenear sides of the structure 20, in such a manner that the upper comb 132results opportunely spaced from the lower comb 128 and that the film mayfreely runs through the so made distributor. On the lower wall of theswinging jaw 32, upstream of the comb 132, there is fixed in relief astrip 37 of rubber and with longitudinal lines. When the distributor isopened as from FIG. 2, the strip 37 is raised and opportunely spacedfrom the lower one indicated with reference numeral 29, and form theferromagnetic disks 38, 38′ fixed to the inferior side of the same jaw32 and centred with electromagnets 31, 31′, are opportunely spaced fromthis latter components de-energized. When, on the contrary, theelectromagnets 31, 31′ are energized, as from FIG. 3, these attract theabove mentioned disks 38, 38′ and cause downwardly oscillation of theportion of the upper jaw 32 which is provided of the rubber strip 38,which blocks the film on the lower rubber strip 29, in contrast with theaction of springs 35, 35′, which are proportionally compressed, in sucha manner to re-open, at the right time, the distributor as theenergization of the said electromagnets 31, 31′ ceases. Suitable meansmay be provided for the partializing of the energization of theelectromagnets, 31, 31′, in order to allow that the film results to bealways transversally seized with pliers in the distributor, but in aposition in which it can suitably run in longitudinal direction. Thiscondition may be, for example especially useful in the phase in whichthe packaging film is transversally pre-stretched by some of the lateralgrippers of the packaging machine.

1. Film folding and supplying apparatus for the machines for thepackaging of products with stretchable film, of the type comprisingguiding means placed between the feeding bobbin of the film and thewrapping station, in order to subject the portion of film cyclicallyinserted in said station, to a possible operation of folding with thefolds oriented in the travelling direction of the film, to modify thewidth of the same film with respect to the dimensions of the product tobe wrapped, in such a manner that the last edges of the film on thebottom of the product, during the normal working cycle of the packagingmachine, do not laterally project from the bottom of the same product,characterised by the fact that said guiding means which provide to thepleating of the wrapping film, are pre-arranged to co-operateessentially with rolling friction with the same wrapping film. 2.Apparatus according to claim 1, characterised by the fact that the meansfor the folding of the wrapping film, are such to give to the same filma substantially omega transversal section.
 3. Apparatus according toclaim 1, characterised by the fact that the means for the pleating ofthe wrapping film, are pre-arranged adjustable for the adjustment tofilms of at least two different widths and to pleat the film with awidth proportionate to the one of the two different ranges ofmedium-small and large products which can be packaged by a same machine.4. Apparatus according to claim 3, characterised by the fact that themeans for the adjusting of the pleating means of the wrapping film, aresuch to pleat the film with a width which is proportionate to the one ofthe products of smaller width of the two different ranges ofmedium-small and large packageable by a same machine.
 5. Apparatusaccording to claim 1, characterised by the fact that the pleating meansof the wrapping film comprise an elongate, flat and fixed guide, whichwith its longitudinal edges carries projecting rows of flat, idle androunded edges wheels, which substitute to said edges of the guide toco-operate with the film with rolling friction, there being providedthat the edges of the film laterally projecting from said central guidecan be partially folded below said row of wheels, by means of theinternal and opportunely bent edges, with progressive reciprocalapproach in the travelling direction of the film, of respective lateralguides which upon said internal edges carry suitably projecting,respective rows of flat, idle and rounded edges wheels, to co-operatewith rolling friction with the wrapping film.
 6. Apparatus according toclaim 5, characterised by the fact that the longitudinal edges of thecentral guide are slightly upwardly bent, in such a manner that the rowsof wheels rotatably placed on the edges are forming, in the whole, anupwardly concave sliding surface, so that the medial portion of the filmin the folding phase does not touch the upper face of said wheels. 7.Apparatus according to claim 5, characterised by the fact that thelongitudinal and internal edges of the lateral guides, are slightlydownwardly bent, so that the rows of wheels rotatably assembled uponsaid edges form in the whole a downwardly convex sliding surface, sothat the edges of the folded film do no touch the lower face of saidwheels.
 8. Apparatus according to claim 5 characterised by the fact thatthe central guide is provided in the terminal and posterior portion ofits lateral edges, with rounded-edges plates made with suitablelow-friction coefficient material, which with the external side are insubstantial tangency condition with the peripheral and active portion ofthe last folding wheels carried by the same lateral edges of said guidein such a manner that said plates concur to told and guide in correctmanner the film during the folding phase.
 9. Apparatus according toclaim 5, characterised by the fact that the central guide with the rowsof lateral wheels is fixed with its center line upon projections carriedby the longitudinal member of an underlying ribbed and a cross plansupport, said longitudinal member being fixed with one end, and inprojecting manner, to the traverse which supports the distributor of thefilm and being downwardly inclined with the other end which isprojecting for a correct portion from the anterior end of said centralguide, under which there is fixed on the central line a support which isrotatably supporting in front of said guide and transversally to this, adouble roller having the same width of the sliding track made by thewheels of said guide and upon which the film slides before reaching onsaid wheels.
 10. Apparatus according to claim 9, characterised by thefact that the anterior end of said longitudinal member of the supportwhich is supporting the central guide of the folding means of the film,ends with a fork conformation to support rotatably free, a centralroller and consecutively to this a couple of lateral and equal rollersangularly spaced from the central roller of about 8-10° degrees, in sucha manner to realise a convex transmission upon which is transmitted thefilm before reaching the folding means, to maintain the same filmopportunely stretched in transversal direction.
 11. Apparatus accordingto claim 5, characterised by the fact that the lateral guides with therelative rows of wheels for the folding of the film, are reinforced bysuitably ribs and carries intermediate appendices for the outsidewidening, provided with slots transversal to the path of the film andcrossed by screws for the fixing of said guides on the flat ends of thearms of said cross-support, in such a manner that it is possible toadjust the distance between the lateral guides with a variation which isequal to the length of said slots.
 12. Apparatus according to claim 11,characterised by the fact that the flat ends of the arms of the crosssupport, which is supporting the guides for the folding of the film, areprovided with couples of threaded holes having a different distance fromthe longitudinal member of the said cross-shaped support and in saidholes may be screwed the fixing screws for the lateral guides, in such amanner that said guides may be adjusted in the reciprocal distance, inaddition to the pitch resulting from the length of said slots, also withthe pitch given by the distance between the said couples of threadedholes.
 13. Apparatus according to claim 9, characterised by the factthat the end of the longitudinal member of the cross-support, which isfixed to the traverse for the support of the film distributor, isenlarged and rotatably supports the intermediate portion of a shaftwhich is horizontal and transversal to the path of the film, upon whichthere are fixed rubber rollers with the same features, upon which thereare sliding the lateral edges of the film which is coming out from thefolding means, the same film being pushed against said rollers by meansof an overhanging parallel roller which because of the utilisation offreewheels, is freely rotatable only in the running direction of thefilm and not in the opposite direction.
 14. Apparatus according to claim9, characterised by the fact that the traverse which supports inprojecting manner the cross support with the folding means of the film,has rounded edges and it is at a such level that upon same may run thefolded film, said traverse being provided on the posterior front for theexit of the film and on the upper wall, with a recess in which there isfixed a jaw with the upper portion comb-shaped, with the teeth openedand oriented accordingly to the running direction of the folded film andupstream of said jaw and parallel to this, said traverse being providedwith a recess having a length which is the same of said jaw, whichhouses in a condition of non-projection a rubber insert withlongitudinal grooves and being provided that the same traverse isprovided at the level of the ends of said jaw, with recesses housingelectromagnets useful for the closure of the film distributor of thefilm inferiorly formed by the above mentioned portions.
 15. Apparatusaccording to claim 14, characterised by the fact that superiorly to thelower comb for the distributor of the film, there is provided acomplementary comb obtained in the lower portion of a traverse with an Llateral shape and suitably ribbed at least at the ends which arefulcrumed on an axle which is parallel to the longitudinal axis of saidcomb and which ideally passes for (by) for the point of the teeth of thesame comb, the said traverse being provided at the ends with appendiceswhich transversally extend same in the running direction of the film andbeyond the point of the teeth of its comb, upon which appendices thereoperate elastic means which push said appendices against lower andadjustable retainers, the whole in such a manner to maintain the uppercomb of the distributor opportunely raised from the lower comb and tomaintain a strip of rubber upwardly fixed on the lower face of the sameupper comb and preferably provided with suitable longitudinal grooves,opportunely raised and distant from the opposed rubber insert of thelower jaw of the same distributor, there being provided that outside ofthe upper comb the jaw which is defining this component, is inferiorlyprovided with ferromagnetic disks, opposed to the lower electromagnetswhich, when are energized, attract said disks and the upper comb, inorder to stop the film between the strips of rubber of the two combs ofthe distributor.
 16. Apparatus according to claim 15 characterised bythe fact that the energization means of the electromagnets of thedistributor of the film may be such to supply a variable energizationaccording to a pre-established program which provides a loosening of theclamping of the film in some working phases of the packaging machine.